Accerts biggest and number one problem is jackwagons working on them don't understand them. Yes the IVA's are a weak spot. Stands for intake valve actuator. They work the intake valves to recirculate the exhaust. Very same function as an EGR valve but different set up.
As far as cams and rocker arm failures. Keep the overhead set and good clean oil. An oil change is less or about the cost of a tank of fuel. How are extended drains saving you a boat load of cash?
The Accert have the strongest bottom end CAT ever designed honestly. A good one is a hands down money maker. One that's been half assed to save money can be costly to get back right. Keep in mind anything with a million miles can break. Overhauled is a long way from new